The prior art stuffing box packing set is commonly formed by at least one packing which is installed within a stuffing box. The stuffing box comprises a bottom, wall belong to a first device and an upper wall belong to a second device. A shaft passes through the first device, the stuffing box and the second device. The shaft is rotatable along an axis thereof. Oil is filled in the stuffing box. However, in this structure, a very good oil seal effect is needed to insure that no oil will flow out of the stuffing box. Therefore, the structure of the packing is very important for assuring the preferred oil sealing effect.
In one prior art, U.S. Pat. No. 5,806,959 discloses a compact five ring stuffing box packing assembly includes high density metal inserted braided and rings of graphite which have each been die formed to have angled facing surfaces. Three low density graphite perform rings having angled facing surfaces are contained between the high density braided end rings. The facing surfaces of the perform rings extend at a different angle relative to the longitudinal axis of the packing assembly than to do the facing surfaces of the braided end rings. The braided end rings provide a support function for the perform rings as well as a stem wiping function.
The above mentioned structure can suffer from the pressure from the upper side, but they cannot effectively disperse the pressure along the radial direction so that when the packing assembly is used for a longer time, the packing pieces of the assembly will be destroyed. As a result, the destroyed piece must be updated and thus the lifetime of the packing is short.